Heat-treating



June 20, 1944. c; LYNN 2,351,987

HEAT-TREATING.

Filed Dec. 3, 1942 WITNESSES: INVENTOR C/arence L ynn I i QMMAMM ATTORNEY Patented June 20, 1944 nm'r-raca'rnsc Clarence Lynn, Pittsburgh, 2a., assignor to Westinghouse Electric 8: Mann! acturing Company,

East Pittsburgh, Pa, a corporation of Pennsylvania Application December 3, 1942, Serial No. 467,726

6 Claims.

This invention relates to the heat-treatment.

of material which is wound into coil form, and has for its main object a rapid end uniform heattreating, more particularly bright annealing, of a coil of metal wire or strip by repeatedly unwinding and rewinding thecoil during the heattreatment.

A form of furnace in which the teachings of my invention may be carried out, to which form, however, I am not necessarily limited, comprises a, base removably carrying an outer metal hood which cooperates with the base to provide a substantially gas-tight heat-treating chamber in'which the coiled strip is completely enclosed. An insulated heating bell carrying any suitable heating means may be placed about the hood for heating the chamber. Rotatably mounted inside this chamber are a pair of reels or spools on one of which the coil of strip is initially placed. The coil is unwound from this reel onto the other reel and when the coil is thus substantially transferred to this 'other reel it is again unwound and rewound on the first reel. This-process is repeated so that the strip passes to and fro between the reels whereby each ele-' ment of the strip is repeatedly exposed in turn to the heat of the furnace without being shielded by other outer layers of the coil through which heat would haveto pass for heating inner layers of the coil. Preferably the strip is moved back and forth at a substantially uniform linear speed so that the strip is evenly heated-up to annealing temperature.

The repeated windings and unwindings of the strip being heatedreduce the time required to bring the coil of strip up to annealing temperature! and reduce temperature gradients through their coiled material so that a considerable savingfin the time of annealing and an improvement in the quality of the annealed strip are obtained in comparison with prior strip-annealing furnaces.

Many other objects, features and innovations .of my invention will be discernible from the following description thereof which is to be I, taken in connection with the accompanying drawing. In the drawing which schematically winding and unwinding of the strip by the reels; Y

and

Fig. 2 is a horizontal section view, on a different scale and with parts omitted, of the heattreating chamber. of the furnace, for further 7 illustrating the coil winding and unwinding reels.

While the teachings of my invention may be applied to the heat-treatment of any coiled metals, for example, wire or strip, in any suitable form of furnace, I illustrate, as a preferred form embodying my invention, a bell furnace which comprises a metal-jacketed base 2 adapted to cooperate with a removable metal hood 4 to provide a heat-treatment chamber 6 in which one or more coils of strip may be placed for heat-treatment, although the furnace is shown herein for simplicity as adapted to heat-'- treat. a single coil.

The chamber 6 is preferably gas-tight and is gas-sealed by a gas-sealing means comprising a base-trough 8, around the periphery of the base 4, containing a gas-sealing medium Ill,

such as sand, into which a peripheral flange l2 depending from a skirt 14 of the hood 4, de-

pends. Any desired controlled atmosphere may be continually conveyed into the heat-treatment chamber 6 through one or more gas-inlet pipes 16 passing through the base 2, near its center; and furnace atmosphere may be vented from the chamber through one. or more gasoutlet pipes l8 at the ends of the chamber, for keeping the atmosphere aboutthe strip clean and pure.

The heat-treatment chamber 6 may be raised to annealing temperature and maintained I thereat for some time, if necessary, by any $111!?- illustrates only a sumcient number of parts necessary for an understanding of my invention:

Fig. l is a view in verticalsection," showin an annealing furnace embodying "my invention,

and further schematicallyshowing a wiring diagram of a control means for controlling the able heating means, but in the form of furnace herein described this means comprises an-outer metal-jacketed heating bell 20 comprising electric heating means 22 carried by its heat-insulating and refractory walls 24; the bell bein remcvably placeable on the horizontal skirt ll of the hood 4 and being supported by the base 2.

Two spaced shafts 26 and 28 pass through the base 2, being rotatably supported in lower bearings 30 and upper gas-sealing bearings 32, these shafts beingpreferably hollow for this particular embodiment, for reasons which will later be apparent. Coiling-turntables 34 and 36 are se- 7 cured for rotation respectively with the shafts 26 and 28. Each turntable is provided with a central non-circular mandrel-receiving indent which receives a mating protruding end 38 of a coil-winding mandrel. Such a mandrel 4|! is provided for the turntable. 34 and a similar Assuming that a coil of strip '55 on the mandrel 55 is to be annealed, the outer free endedge of the strip is secured to the mandrel 42 and while the heat-treating means or bell 25 is raising the temperature of the heat-treatment chamber 5, the shaft 25 is' revolved in a direction to unwind the strip from the. mandrel 45 and wind it as a coil on the mandrel 52. After the winding is substantially completed the shaft is rotated to rewind the strip on the mandrel 55; and the transfer of the coil, by winding, from 15 each mandrel to the other is repeated, during the time the temperature of the strip is being raised, as often as desired, but preferably the strip should make a few passes between the two mandrels during a heating-up'treatment. Durgo ing cooling of the strip, with the heating bell removed, the unwinding and rewlnding of the strip can be continued if desired. Where soaking at a ed temperature is necessary, the strip may 0 viously be caused to similarly travel back and 2 forth between reels, or may be stationary.

The heating of stationary coiled strip from about room to annealing temperatures in conven-. tional furnaces is commonly considered to require about an hour and a half per inch of radial thickness of the coil so that an-eight inch thick coil, on this basis, requires about twelve hours to be brought up to annealing temperature. By causing the strip to be passed back and forth repeatedly and successively between the coil winding mandrels and 52 this time is decreased considerably, to as little as four hours and less, as a particular but not limiting example, other conditions being the same. The strip need not be moved at a high rate of speed, and as little as 15 40 feet per minute and even less is satisfactory; although it is obvious that the higher the linear speed of the strip the more uniform will be the temperature throughout the coil unlessthe speed is so high that the strip-span does not have time to heat significantly. For the same size coils, the strip speed should be somewhat higher with thinner strip; but about four passes of the strip between mandrels are generally satisfactoryror annealing although the number of passes can obviously be considerably more, and even less, dependent, to some degree, on the'capacity of the strip to absorb heat and the tolerable temperature gradient through the coil.

Heating the strip in the manner described has 55 the further advantage of more rapidly removing burnable or volatile substances from the surface of the strip.

The coil winding and unwinding operations may be carried out by hand or automatically by vibrating relay 51 and the machine 5| acting as a braking generator the power of which is conany suitable control means. when an automatic control means is provided it is also desirable to choose one which will move the strip at a substantially constant linear speed.

In Figure 1, a control means is shown which 55 controls both the direction of rotation of the different shafts 25 and 25 and the linear speed of travel of the strip. This means-comprises a direct-current dynamo-electric machine 55 geared to the shaft 25, and a similar dynamo-electric tor; and conversely when the coil is being wound 15 on the mandrel 42 driven by the shaft 25, the machine 5| acts as a motor and the machine 55 as abraking generator.

The control means for selecting the function of the dynamo-electric machines and controlling them so that the linear speed of movement of the strip is substantially constant comprises limit I switch means operable for interchanging the functions of the machines when the strip is substantially unwound from a mandrel. A specific form of such travel limit switch means is herein disclosed comprising a switch operating, device associated with each mandrel. Each such device comprises a small slot 52 in the associated man-- drel, in which an edge 53 protruding from a bellcrank 54, is urged or forced outwardly by a compression spring 55 acting upwardly through a rod; j

55, passing through the associated hollow driving shaft, the rod being pivoted to one end of an arm 51 of the bell-crank, the other end of the arm being pivoted as at 58. So long as there is strip around the mandrel, as shown at the right of.

Fig. 1, the protruding edge 53 on'the bell-crankcannot pass beyond the slot 52. However, when the strip is substantially unwound so that the strip no longer obstructs movement of the bell pairof contacts 52 and a coil 53 being controlled 4 by therod 55 associated with the mandrel 52 and the machine 5|.

When strip is being wound on a mandrel, the first turn or part turn of the strip pushes the Fig. 1) pairs of contacts 55 when the coil 53 is energized, .the bars 54 remaining in such position untilthe coil 5| is energized whereupon they are moved to the left, in the position shown, bridging the pairs of contacts 55.

In one position of the two position relay 59 the dynamo-electric machine 5| operates as a motor for winding the strip onto the mandrel 42, the

speed of operation of the motor being controlled by a vibrating relay 51 and a plurality of current controlling resistors in the motor circuit; and the dynamo-electric machine 55 operates as a braking generator feeding a load 55, the generator power being controlled by a vibrating relay 55. In the other position of the two position relay 55 the functions of the dynamo-electric machines 55 and 5| are reversed, the machine 50 acting as a motor the power of which is controlled by the trolled by the vibrating 'relay 59.

,The motor-controlling vibrating relay 51 and the circuits controlled thereby cause the machine acting asa motor to deliver a substantially constant amount of power irrespective of the varying diameter of the coil of strip being wound thereby, and in the same way'the generator-controlling vibrating relay 59 anclassociated circuits cause the braking power of the machine acting as a generator to be substantially constant irrespective of the varying diameter of the coil of strip. on the unwinding mandrel to which it is mechanically coupled. Thusthe tension on the strip is controlled for causing a substantially constant linear speed of travel of the strip between the mandrels.

A control means of the type mentioned is more completely shown, described and claimed in the W. H. Landerberger Patent No. 1,869,900 of August 2, 1932, assigned to the Westinghouse Electric 8: Manufacturing Company.

While I have described my invention as applied to a specific form of furnace, which I consider a desirable preferred form, it is obvious that the teachings of my invention are of considerably greater general application and may be applied to other forms of furnaces and with reels disposed other than vertically.

I claim as my invention; 1. Annealing equipment for annealing a coil of strip, comprising, in combination, a substantially enclosed chamber means, heating means for heating said chamber means, coil winding and unwinding means comprising a pair of rotatable means in spaced relation in said chamber means, said pair of rotatable means being subject to the heat in said chamber means, each of said rotatable means being of a size sumcient to carry a coil of material to be heat-treated in said chamber means, and tension control means associated with said coil winding and unwinding means for controlling the tension of the material being passed between said pair of rotatable means.

2. Means for annealing coiled strip, compris- I ing the combination of substantially enclosed heat-treating chamber means for the strip. a pair of spaced rotatable means in said chamber means, adapted to have different end-edges of the strip respectively secured thereto, and means for causing rotation of said rotatable means in a manner to unwind strip coiled on a first of said rotatable means and wind it on the other of said rotatable means, the last said means including control means for causing the strip to move between said rotatable means at a substantially constant linear speed, whereby said strip will be more uniformly heat-treated. I

3. For a furnace for annealing coiled strip, means comprising the combination of a heattreating chamber for the strip. said chamber having a base, a pair of spaced rotatable means in said chamber adapted to have different endedges of the strip respectively secured thereto. and means for causing rotation of said rotatable means in a manner to unwind strip coiled on either of said rotatable means and wind it on the other of said rotatable means, the last said means comprising control means automatically operable when the strip is substantially unwound from either of said rotatable means to cause the strip to rewind thereon, whereby the strip is re;- peatedly passed back and forth between said pair of rotatable means during a heat-treatment in a said chamber, the said control means including means for causing the strip to move at a substantially constant linear speed while passing between said rotatable means.

4. The structure of claim 3 characterized by. the last said means includingmeans for rotating said rotatable means in a manner for controlling the tension on the strip spanning said rotatable means.

5. A bell furnace for rapidly and uniformly annealing coiled strip, comprising, in combination, a base, a removable metal hood associated with said base to provide an enclosed heat-treating chamber, a removable heating bell associated with said hood for causing said chamber to be heated, a pair of spaced shafts passing through said base, each of said shafts having a coilingmandrel rotatable therewith, driving means for.

rotating said shaft whereby strip initially coiled 6. The method of on one of said coiling-mandrels will be automatically and successively passed between said coiling-mandrels, said driving means including control means for controlling the rotation of said coiling-mandrels in a manner for controlling the tension on the span of strip between the coilingmandrels.

of a gas-filled heating chambef'zwhich-"comprises repeatedly coiling and uncoiling the strip inside the chamber with the strip portionsextendingi 1 between the coiled and uncoiling parts of the strip moving at substantially a constant linear speed.

CLARENCE LYNN.

annealing boiled-strip. inside 

